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.TH MKFIFO 3C "June 18, 2021"
.SH NAME
mkfifo, mkfifoat \- make a FIFO special file
.SH SYNOPSIS
.nf
#include <sys/types.h>
#include <sys/stat.h>

\fBint\fR \fBmkfifo\fR(\fBconst char *\fR\fIpath\fR, \fBmode_t\fR \fImode\fR);
.fi
.LP
.nf
\fBint\fR \fBmkfifoat\fR(\fBint\fR \fIfd\fR, \fBconst char *\fR\fIpath\fR, \fBmode_t\fR \fImode\fR);
.fi

.SH DESCRIPTION
The \fBmkfifo()\fR and \fBmkfifoat()\fR functions create a new FIFO special file
named by the pathname pointed to by \fIpath\fR.  The file permission bits of the
new FIFO are initialized from \fImode\fR.  The file permission bits of the
\fImode\fR argument are modified by the process's file creation mask (see
\fBumask\fR(2)).  Bits other than the file permission bits in \fImode\fR are
ignored.
.sp
.LP
If \fIpath\fR names a symbolic link, \fBmkfifo()\fR and \fBmkfifoat()\fR fail
and set \fBerrno\fR to \fBEEXIST\fR.
.sp
.LP
The FIFO's user ID is set to the process's effective user ID. The FIFO's group
ID is set to the group ID of the parent directory or to the effective group ID
of the process.
.sp
.LP
The \fBmkfifoat()\fR function is equivalent to \fBmkfifo()\fR; however, if
\fIpath\fR is a relative path, then it is resolved start at the directory
represented by \fIfd\fR. \fIfd\fR may be set to the special value of
\fBAT_FDCWD\fR which indicates that the current working directory should be used
to start resolving \fIpath\fR.
.sp
.LP
The \fBmkfifo()\fR function calls \fBmknod\fR(2) to create the file. The
\fBmkfifoat()\fR function calls \fBmknodat\fR(2) to create the file.
.sp
.LP
Upon successful completion, \fBmkfifo()\fR and \fBmkfifoat()\fR mark for update
the \fBst_atime\fR, \fBst_ctime\fR, and \fBst_mtime\fR fields of the file. Also,
the \fBst_ctime\fR and \fBst_mtime\fR fields of the directory that contains the
new entry are marked for update.
.SH RETURN VALUES
Upon successful completion, \fB0\fR is returned.  Otherwise, \fB\(mi1\fR is
returned and \fBerrno\fR is set to indicate the error.
.SH ERRORS
The \fBmkfifo()\fR and \fBmkfifoat()\fR functions will fail if:
.sp
.ne 2
.na
\fB\fBEACCES\fR\fR
.ad
.RS 16n
A component of the path prefix denies search permission, or write permission is
denied on the parent directory of the FIFO to be created.
.RE

.sp
.ne 2
.na
\fB\fBEEXIST\fR\fR
.ad
.RS 16n
The named file already exists.
.RE

.sp
.ne 2
.na
\fB\fBELOOP\fR\fR
.ad
.RS 16n
A loop exists in symbolic links encountered during resolution of the \fIpath\fR
argument.
.RE

.sp
.ne 2
.na
\fB\fBENAMETOOLONG\fR\fR
.ad
.RS 16n
The length of the \fIpath\fR argument exceeds {\fBPATH_MAX\fR} or a pathname
component is longer than {\fBNAME_MAX\fR}.
.RE

.sp
.ne 2
.na
\fB\fBENOENT\fR\fR
.ad
.RS 16n
A component of the path prefix specified by \fIpath\fR does not name an
existing directory or \fIpath\fR is an empty string.
.RE

.sp
.ne 2
.na
\fB\fBENOSPC\fR\fR
.ad
.RS 16n
The directory that would contain the new file cannot be extended or the file
system is out of file-allocation resources.
.RE

.sp
.ne 2
.na
\fB\fBENOTDIR\fR\fR
.ad
.RS 16n
A component of the path prefix is not a directory. For \fBmkfifoat()\fR,
\fIpath\fR is a relative path and \fIfd\fR is a valid file descriptor which is
not a directory.
.RE

.sp
.ne 2
.na
\fB\fBEROFS\fR\fR
.ad
.RS 16n
The named file resides on a read-only file system.
.RE

.sp
.LP
The \fBmkfifoat()\fR function will fail if:
.sp
.ne 2
.na
.B EBADF
.ad
.RS 16n
The \fIpath\fR argument is a relative path and \fIfd\fR is not a valid file
descriptor or the value \fBAT_FDCWD\fR.
.RE

.sp
.LP
The \fBmkfifo()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBELOOP\fR\fR
.ad
.RS 16n
Too many symbolic links were encountered in resolving \fIpath\fR.
.RE

.sp
.ne 2
.na
\fB\fBENAMETOOLONG\fR\fR
.ad
.RS 16n
The length of the \fIpath\fR argument exceeds {\fBPATH_MAX\fR} or a pathname
component is longer than {\fBNAME_MAX\fR}.
.RE

.SH EXAMPLES
\fBExample 1 \fRCreate a FIFO File
.sp
.LP
The following example demonstrates how to create a FIFO file named
\fB/home/cnd/mod_done\fR with read and write permissions for the owner and read
permissions for the group and others.

.sp
.in +2
.nf
#include <sys/types.h>
#include <sys/stat.h>
int status;
\&...
status = mkfifo("/home/cnd/mod_done", S_IWUSR | S_IRUSR |
        S_IRGRP | S_IROTH);
.fi
.in -2

.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.BR mkdir (1),
.BR chmod (2),
.BR exec (2),
.BR mknod (2),
.BR umask (2),
.BR stat.h (3HEAD),
.BR ufs (4FS),
.BR attributes (7),
.BR standards (7)
